1. Field of the Invention
The present invention relates to a touch panel, and more particularly, to a touch sensing circuit and a touch sensing method capable of really determining multiple touch points on the capacitance touch panel by sensing the equivalent capacitances.
2. Description of the Prior Art
In general, the touch panels can be divided into different types, such as the resistance type, the capacitance type, the ultrasonic type, optical type, according to their sensing theorems. Wherein, the capacitance touch panel can sense a slight touch, and there is almost no wearing damage generated by the touch between the finger and the touch panel, so that it is stable and has long life. Therefore, compared to the conventional resistance type touch panel,
Please refer to FIG. 1A and FIG. 1B. FIG. 1A and FIG. 1B show the conventional touch sensing circuit 1 and its control signal input timing diagram. As shown in FIG. 1A and FIG. 1B, the conventional touch sensing circuit will orderly input pulsed square waves from the signal input module 12 to the touch pads X1˜X6 and Y1˜Y6 on the touch panel from the X-axis direction to the Y-axis direction (or from the Y-axis direction to the X-axis direction) in a time sharing way. Then, the sensing module 14 will sense the change of the parasitic capacitance generated when the pointing object (e.g., a finger or a touch pen tip) touches the panel, and further detect the touch action of the user and the position of the touch point formed on the panel.
However, when the user performs multiple touches on the capacitance type touch panel, the above-mentioned conventional sensing circuit structure and its sensing method will only sense the range of the touch points, but fail to determine the real positions of the touch points. For example, when the user uses two fingers to touch the capacitance touch panel, the conventional sensing circuit will detect two maximum values of the parasitic capacitance changes. However, since these two maximum values can be generated through two different touch ways, the system can not precisely determine it is which one of the two ways, and these points not really touched are called “ghost points”.
FIG. 2A and FIG. 2B show scheme diagrams of the conventional touch sensing circuit sensing two touch points. As shown in FIG. 2A, if the user forms two touch points A and B on the touch panel 10, the sensing circuit will detect two maximum values of the parasitic capacitance changes on the X-axis, and also detect two maximum values of the parasitic capacitance changes on the Y-axis. At this time, the touch sensing circuit fails to determine the above-mentioned parasitic capacitance changes are caused by the two touch points A and B, or the two touch points A′ and B′. The touch points A′ and B′ shown in FIG. 2A are ghost points. Similarly, as shown in FIG. 2B, when the user forms two touch points C and D on the touch panel 10, two ghost points C′ and D′ will be generated.